This invention relates to collision warning systems for motor vehicles and in particular to an antenna cluster for use in such a collision warning system.
Various different types of collision warning systems have been proposed for motor vehicles which will warn of potential collision with moving targets, primarily other vehicles and stationary obstacles especially when parking. Such systems include "closing vehicle same lane warning systems" for looking behind a vehicle when it is traveling forwards for noting when a vehicle is approaching from the rear; parking aids for looking forwards when the vehicle is traveling slowly forwards and backwards when the vehicle is traveling slowly backwards; backup aids; short range frontal collision warning systems for looking ahead of the vehicle while driving forwards; parking space measuring aids for measuring the length of a parallel parking space to the side of the vehicle; driver induced impaired visibility aids to help ensure that the driver can notice vehicles approaching his side in an overtaking lane; side vision aids for looking to the side of the vehicle; and lane change aids for checking that the driver is free to overtake, or indeed move to an inside lane.
Typically these have all been designed as discrete packages and so a vehicle having a multiplicity of these aids includes a plurality of sensors of different types and ranges looking around the vehicle.
There are many different types of sensors available including radar and ultrasound sensors which are chosen depending upon the range required for the sensor. The majority of sensor types transmit a signal which is reflected from an obstacle and then received. Measurement of the time delay between transmission and receipt of the signal allows the position of the obstacle to be calculated.
The common features of the above collision warning systems are that they include a sensing system, which has at least one sensor with a field of view in which it may detect an obstacle, and a warning control system which receives "obstacle of concern" signals from the sensor and analyzes them to determine whether a collision warning signal should be generated. However, for each application and at any one time only obstacles in a particular area, known as the zone of concern, are of particular interest. For example, in the parking aid system, as the vehicle moves forward the area to the front and sides of the vehicle is the zone of concern. During reversing, the rear of the vehicle is of primary concern.
A collision warning system for a motor vehicle which is capable of acting as a multifunctional system is described in the applicants previous PCT application PCT/GB97/01728 in which each of the plurality of sensors has a predetermined field of view in which it is capable of detecting obstacles and an instantaneous field of view within which obstacles sensed by the sensor causes the obstacle sensing system to generate an obstacle signal. A vehicle operation sensing means detects at least one property of the vehicle's operation. A zone of concern control means defines a zone of concern within which sensed obstacles trigger the generation of an obstacle of concern signal whereby the zone of concern is defined in dependence on the property or properties of the vehicle's operation sensed by the vehicle operation sensing means. The zone of concern control means controls the sensors such that the instantaneous field of view of the sensors together cover the zone of concern.
The foregoing system includes four sensors which each comprise a transmitter antenna and a receiver antenna. The present invention relates to an antenna cluster especially suitable for use in such a system.